Processes

Hardening (austenitizing) - is defined as the process of forming austenite by heating a ferrous alloy above the transformation range. When used without qualification, the term implies complete austenitizing. Under no circumstances is austenitizing a complete process, but rather it is the initial step prior to normalizing, full annealing of ferrous alloys or quench hardening of ferrous alloys. Austenite is a phase of a ferrous allow that generally exists only at elevated temperatures.
Quench - is the rapid cooling of a steel or alloy from the austenitizing temperature by immersing the workpiece in a liquid or gaseous medium. Quenching media commonly used include water, brine solutions, caustic solutions, oil, polymer solutions, or gas (usually air or nitrogen)
Tempering - In heat treating of ferrous alloys, tempering consists of reheating the austenitized and quench-hardened steel or iron to some preselected temperature that is below the lower transformation temperature (usually below 1300F). Tempering offers a means of obtaining various combinations of mechanical properties. Tempering temperatures used for hardened steels are often no higher than 1300F. The term - tempering - should not be confused with either process annealing or stress relieving. Even though time and temperature cycles for these processes may be the same, the conditions of the materials being processed and the objective may be different.

Neutral Quench & Temper - is the same as stated on the quench & temper tab with the exception of a protective carbonaceous atmosphere that is established by the base carbon of the material to minimize decarburization and/or eliminate any scaling of the parts prior to the quench.

Sub-Critical Annealing - As implied, the term sub-critical means the process is performed below (sub) the A1 transformation temperature. For steel, this temperature is typically around 1330F. For the cast irons that we process, this temperature is usually between 1240F and 1450F. We try to heat the parts to within 10 degrees F of this temperature and hold for a specified period of time.

Isothermal Annealing - This process produces basically the same results as a full annealing in less time and consequently less cost to the customer. Isothermal annealing consists of heating the metal above the upper critical A3 and ACM temperature for steel and above the A1 for cast iron and holding for the specified time. Then we cool the parts to a specified temperature and hold again for the specified time. The typical temperatures for this process are; Heat to between 1600 - 1700F and hold, then cool to between 1000 - 1300F and hold again for the specified time.

Stress Relief - This process is used to relieve stresses that remain locked in a structure as a consequence of a manufacturing process. Stress relief heat treating is the uniform heating of a structure, or portion of a structure, to a temperature below the transformation temperature A1 (for steels and cast iron). For ductile iron, this process is a low temperature treatment used to reduce or relieve internal stresses remaining after casting. The stress relieving of ductile iron castings is carried out at temperatures between 950 and 1250F depending on the type of iron, the time at temperature will depend on the temperature used. For steels, the stress relieving is done at temperatures between 900 and 1250F and the time is varied depending on the temperature used.

Critical Range Anneal - As implied, the term critical range means the process is performed between the A1 and A3 transformation temperature. For steel, this temperature is typically around 1330F. For the cast irons that we process, this temperature is usually between 1240F and 1450F. We try to heat the parts to within 10 degrees F of this temperature and hold for a specified period of time.

Graphitize Anneal - Annealing a ferrous alloy in such a way that some or all of the carbon is precipitated as graphite. When this is formed later by heat treament it is also know as secondary graphitization.

Carbide Removal - Also known as High Temperature annealing. This is a process done well above the upper critical temperature for cast irons. The purpose of which is to breakdown or decompose the carbides formed during cooling. The process is followed by slow cooling well below the critical range.

Normalizing - The purpose of Normalizing varies considerably. Normalizing may increase or decrease the strength and hardness of a given steel depending on the history of the metal. In general, normalizing will make the steel harder and stronger than when it is annealed. Improved machinability, grain structure refinement, homogenization and modification of residual stresses are among the reasons normalizing is done. For some applications, normalizing may be the final heat treatment. This process consists of heating the metal to some temperature above its specific upper transformation temperature. The normalizing temperature used is typically 50 to 100F above this upper transformation temperature and for our purposes is usually between 1600 and 1750F. This is followed by cooling in still or agitated air to at least some temperature below its transformation temperature range. For low-carbon steels, the resulting structure and properties are the same as those produced by full annealing with slightly higher hardness. Normalizing is usually used as a conditioning treatment for refining the grains of steel that have been heated to high temperatures for forging and other hot working operations. The normalizing process is most often done to provide consistent machinability. The normalizing process is usually succeeded by another heat treating operation like austenitizing for hardening.

Tempering - In heat treating of ferrous alloys, tempering consists of reheating the austenitized and quench-hardened steel or iron to some preselected temperature that is below the lower transformation temperature (usually below 1300F). Tempering offers a means of obtaining various combinations of mechanical properties. Tempering temperatures used for hardened steels are often no higher than 1300F. The term -tempering- should not be confused with either process annealing or stress relieving. Even though time and temperature cycles for these processes may be the same, the conditions of the materials being processed and the objectives may be different. Spheroidize Anneal - Heating and cooling to produce a spheroidal or globular form of carbide in steel. This process will produce maximum softness in steel.